Process for the recovery of boron halides from gaseous mixtures



United States Patent O 3,331,663 PROCESS FOR THE RECOVERY OF BORONHALIDES FROM GASEOUS MIXTURES Carl B. Linn, Prairie Village, Kans., andGeorge L. Hervert, Downers Grove, Ill., assiguors to Universal OilProducts Company, Des Plaines, 111., a corporation of Delaware NoDrawing. Original application Oct. 16, 1961, Ser. No. 145,456, nowPatent No. 3,203,764, dated Aug. 31, 1965. Divided and this applicationJune 1, 1965, Ser.

7 Claims. (Cl. 23-405) This is a division of application Ser. No.145,456, filed Oct. 16, 1961, now Patent No. 3,203,764.

This invention relates to a process for the separation and recovery of aboron halide from substantially anhydrous fluid mixtures, and moreparticularly relates to a process for the separation and recovery of aboron halide from substantially anhydrous fluid mixtures with a boronhalide reactant comprising a metal halide. Still more particularly, thisinvention relates to a process for the separation and recovery of aboron halide from substantially anhydrous fluid mixtures with a boronhalide reactant comprising a metal halide thereby reacting at least aportion of said boron halide with said metal halide, and subsequentlyrecovering boron halide from said process.

The term reaction means a mechanism by which at least one component of amixture selectively combines in some form with the solid or solids withwhich the mixture is contacted; such mechanisms may be adsorption,absorption, clathration, occlusion or chemical reaction, and all thesemechanisms are generically designated herein as reaction.

We have found that in the production of alkylated aromatic hydrocarbonsutilizing a boron trifluoridemodified substantially inorganic oxide,alkylatable aromatic hydrocarbon, olefin-acting compound, and borontrifluoride, free boron fluoride will usually be found among the liquidhydrocarbon reaction products and unreactive off-gases. The recovery andreuse of boron fluoride, therefore, results in extraordinary economy ofoperation.

The principal object of the present invention is to provide a processfor the eificient and economical separation and recovery of the boronfluoride from substantially anhydrous fluid mixtures. Another object ofthis invention is to provide a process whereby the boron halide can beseparated continuously fromthe hereinbefore mentioned hydrocarbonreaction products without appreciable consumption and loss of therecovered boron halide. Other objects of this invention will be setforth hereinafter as part of the specifications and in the accompanyingexamples.

In one embodiment, the present invention relates to a process for theseparation and recovery of a boron halide from substantially anhydrousfluid mixtures containing the same, which comprises contacting saidfluid mixtures with a boron halide reactant comprising a metal halidethereby reacting at least a portion of said boron halide with said metalhalide, and subsequently recovering boron halide from said process.

Another embodiment of the present invention relates to a process for theseparation and recovery of a boron halide from a substantially anhydrousgaseous mixture containing the same, which comprises contacting saidgaseous mixture with a boron halide reactant comprising a metal halidethereby reacting at least a portion of said boron halide with said metalhalide, and subsequently recovering boron halide from said process.

A further embodiment of the present invention relates to a process forthe separation and recovery of a boron halide from a substantiallyanhydrous liquid hydrocar bon containing the same, which comprisescontacting said liquid hydrocarbon with a boron halide reactantcomprising a metal halide thereby reacting at least a portion of saidboron halide with said metal halide, and subsequently recovering boronhalide from said process.

A specific embodiment of the present invention relates to a process forthe separation and recovery of boron fluoride from a substantiallyanhydrous gaseous mixture containing the same, which comprisescontacting said gaseous mixture with a boron fluoride reactant selectedfrom the group consisting of a fluoride of a metal from Groups VI, VIIand VIII of Period 4 of the Periodic Table, thereby reacting at least aportion of said boron fluoride with said metal fluoride, andsubsequently recovering boron fluoride from said process.

A further specific embodiment of the present invention relates to aprocess for the separation and recovery of boron fluoride from asubstantially anhydrous gaseous mixture containing the same whichcomprises contacting said gaseous mixture with a boron fluoride reactantcomprising ferrous fluoride in a reaction zone at reaction conditionsincluding a temperature of from about 0 to about 300 C. and a pressureof from about atmospheric to about 200 atmospheres, thereby reacting atleast a portion of said boron fluoride with said ferrous fluoride, andsubsequently recovering boron fluoride from said process.

Another embodiment of the present invention relates to a process for theseparation and recovery of boron fluoride from a substantially anhydrousliquid hydrocarbon containing the same, which comprises contacting saidliquid hydrocarbon with a boron fluoride reactant selected from thegroup consisting of a fluoride of a metal from Groups VI, VII and VIIIof Period 4 of the Periodic Table in a reaction zone at reactionconditions including a temperature of from about 0 to about 300 C. and apressure of from about atmospheric to about 200 atmospheres, therebyreacting at least a portion of said boron fluoride with said metalfluoride, and subsequently recovering boron fluoride from said process.

A still further specific embodiment of the present invention relates toa process for the separation and recovery of boron fluoride fromsubstantially anhydrous liquid benzene containing the same, whichcomprises contacting said liquid benzene with a boron fluoride reactantcomprising chromous fluoride in a reaction zone at reaction conditionsincluding a temperature of from about 0 to about 300 C. and a pressureof from about atmospheric to about 200 atmospheres, thereby reacting atleast a portion of said boron fluoride with said chromous fluoride, andsubsequently recovering boron fluoride from said process.

Other embodiments of the present invention will become apparent inconsidering the specification as hereinafter set forth.

As set forth hereinabove, the present invention relates to a process forthe separation and recovery of a boron halide from substantiallyanhydrous fluid mixtures utilizing a boron halide reactant comprising ametal halide as the reacting agent. Many suitable metal halides areutiliza'ble as reaction agents in the process of this invention. Ingeneral, metal halides in which the metal is dior trivalent and ispresent in the low or intermediate valence state appear to be moreeffective and are preferred. These compounds include such substances asthe halides of the metals of Groups VI, VII and VIII of the PeriodicTable, such as chromous fluoride, chromous chloride, manganesedifluoride, manganese dichloride, ferrous fluoride, ferrous chloride,cobaltous fluoride, cobaltous chloride, nickelous fluoride, etc. Of theabove-mentioned metal halides, ferrous fluoride is preferred as thereaction agent for recovering boron fluoride.

Many fluid mixtures can be substantially purified utilizing the processof this invention. Typical gaseous mixtures include such components ashydrogen, methane,

normal hexane, etc. Typical cycloparaflins are cyclopentane,methylcyclopentane, cyclohexane, methylcyclohexane, cycloheptane,cyclooctane, etc. Typical aromatic hydrocarbons include benzene,toluene, orthoxylene, metaxylene, para-xylene, ethylbenzene,ortho-ethyltoluene, meta-ethyltoluene, para-ethyltoluene,1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene,diethylbenzenes, triethylbenzenes, normal propylbenzenes,isopropylbenzenes, etc. Preferred hydrocarbons are monocyclic aromatichydrocarbons, that is, benzene hydrocarbons. Higher molecular weightalkyl aromatic hydrocarbons are also suitable. These include thosearomatic hydrocarbons such as are pnoduced by the alkylation of aromatichydrocarbons with olefin polymers and are used as intermediates in thepreparation of sulfonate surface-active agents. Such products arefrequently referred to in the art as alkylate, and includehexylbenzenes, nonylbenzenes, dodecylbenzenes, pentadecylbenzenes,hexyltoluenes, nonyltoluenes, dodecyltoluenes, pentadecyltoluenes, etc.Very often alkylate is obtained as a high boiling fraction in which thealkyl group attached to the aromatic nucleus varies in size from about Cto C Other typical aromatic hydrocarbons, which at specified reactionconditions, depending upon the melting point of the aromatic chosen,would be in liquid form, would include those aromatic hydrocarbons withtwo or more aryl groups such as diphenyl, diphenylmethane, naphthalene,triphenyl, triphenylmethane, fluorene, stilbene, etc. Examples of otheraromatic hydrocarbons within the scope of this invention which atspecified reaction conditions, depending upon the melting point of thearomatic chosen, would be in liquid form, include those containingcondensed aromatic rings. These include naphthalene, alkylnaphthalenes,anthracene, phenonthrene, naphthacene, rubrene, etc. Of theabovementioned aromatic hydrocarbons that could be utilized in theprocess of this invention, the benzene hydrocarbons are preferred, andof the preferred benzene hydrocarbons, benzene itself is particularlypreferred.

In accordance with the process of the present invention, the separationand recovery of boron halide from substantially anhydrous fluid mixturesis effected by contacting said fluid mixtures with a boron halidereactant comprising a metal halide at a temperature of from about C. orlower to about 300 C. or higher, and preferably from about C. to'about70 C., although the exact temperature needed will depend upon theparticular fluid to be purified and the particular metal halideutilized. The lower temperature limit is one at which the metalhalide-boron halide complex is stable, while the upper temperature limitlies below the decomposition temperature of the metal halide-boronhalide complex. The reaction process is usually carried out at apressure of from about atmospheric to about 200 atmospheres. Thepressure utilized is usually selected to effect the desired selectivereaction. The reaction bed is then periodically regenerated for use byheating the boron halide-saturated metal halide to a temperature abovethat used during reaction and preferably about 150 C. when the reactiontemperature is below 150 C. where boron halide is evolved and the metalhalide regenerated for reuse. The decomposition of the boronhalide-saturated metal halide may be conducted in the presence of thefluid mixture if desired.

In separating the hereinbefore mentioned boron halide .from asubstantially anhydrous fluid mixture with the type of reaction mediaherein described, either batch or continuous operations may be employed.Although the invention is particularly applicable to the separation andrecovery of boron fluoride from gaseous mixtures it may also be used forthe separation of boron chloride or other tane, isobutane, normalpentane, isopentane, neopentane,

boron halides from such mixtures when present alone or in admixture withboron fluoride. The actual operation of the process may be either upflowor downflow. The details of processes of this general character arefamiliar to those skilled in the art and any necessary additionsormodifications of the above general procedures will be more or lessobvious and can be made without departing from the broad scope of thisinvention.

The process of the present invention is illustrated by the followingexamples which are introduced for the purpose of illustration only andwith no intention of unduly limiting the generally broad scope of theinvention.

Example I This example illustrates the effectiveness of the separationand recovery of a boron halide from a substantially anhydrous fluidmixture utilizing the process of the present invention. 7 g

The following technique was involved. Sixty milliliters of the boronhalide reactant, namely ferrous fluoride deposited on charcoal, wasplaced in a reaction zone forming a bed 6 /2 inches in length. A 2.86weight percent boron trifluoride-balance nitrogen mixture was passeddownflow through the reactant at 425 p.s.i.g. and 25 C. The gas flowrate equalled from 0.170.l cubic foot per hour at 0 C. and 760 mm. Afterdepressuring the reaction zone to determine if any of the borontrifluoride reacted could be liberated by a pressure difference, theboron trifluoride recovery cycle was started. It consisted ofdetermining the amounts of boron trifluoride which could be liberated atvarious temperatures while flushing with high surface sodium-driednitrogen.

The boron trifluoride pick-up by the boron halide reactant wascalculated from the amount of nitrogen exiting from the reaction zoneminus any boron trifluoride contained therein. The amount of borontrifluoride picked up during the depressuring portion of the cycle wasif1= cluded in the total boron trifluoride pick-up. In all cases, thisgas was passed through a series of three stainlesssteel scrubberscontaining iced water. The resulting scrubber solutions were analyzedfor boron content by spectrophotometric measurement of the absorbance ofthe complex of carminic acid and boron.

As shown in the summary of Test 1 in Table I, boron trifluoride wascompletely removed from the 2.86 weight.

with unreacted ferrous fluoride further down the bed and thus escapeddetection.

Asindicated in portions (a) and (b) of the recovery cycle shown in TableI, the ferrous fluoborate did not appreciably dissociate at 24- C. and100 C. respectively while passing dry nitrogen through the bed in orderto remove the boron trifluoride. However, at 200 C., the rate of borontrifluoride liberation was at least three fold that at 100 C., asindicated in portions (0) and (d) of the recovery cycle. Approximately52% of the boron trifluoride picked up was recovered during the cycle.

As shown in the summary of Test 2 in Table I, the boron trifluoridereaction cycle was repeated at about similar conditions. Although 25milligrams of boron trifluoride (of 2,189 charged) was accounted for inthe exit gas from the reaction zone during this part of the trifluoridepick-up was still in excess of 99 weight percent.

The boron trifluoride recovery cycle'was effected at.

a temperature 50 lower than the previous cycle in order to eliminateremoval of any boron trifluoride remaining from the first recoverycycle, which was carried out at 200 C. The recovery of the borontrifiuoride from this latter reaction cycle amounted to 79.6% of thatoriginally picked up. Most of the boron trifiuoride (78.5% of thatpicked up) was released during the first sixteen hours of the recoverycycle at 150 C., as indicated in portion (2) of the recovery cycle;thereafter, under similar conditions for twelve hours, only 1.1% of theboron trifiuoride picked up was released, as indicated in portion (1) ofthe recovery cycle. The more complete removal of the boron trifiuoridefrom the ferrous fluoride reaction agent probably occurred afterequilibrium was established between the charcoal and the borontrifiuoride.

6 general processing technique as utilized in Examples I and II are alsoused in this example.

Sixty milliliters of the boron halide reactant, namely ferrous fluoridedeposited on charcoal, is placed in the reaction zone. The substantiallyanhydrous liquid hydrocarbon containing boron trifiuoride, namelybenzene, is passed downflow through the reactant at 500 p.s.i.g. and 50C. After depressuring the reaction zone to determine if any of the borontrifiuoride reacted could be liberated by a pressure difference, theboron trifiuoride recovery cycle is started. The amounts of borontrifiuoride liberated at various temperatures are determined whileflushing with high surface sodium-dried nitrogen.

TABLE I.UTILIZATION OF FERROUS FLUORIDE AS REACTION AGENT Boron HalideReactant-Ferrous Fluoride on Charcoal Fluid Mixturc zfifi Wt. Percent BF97.14 Wt. Percent N,

BF3, mg. Temp., Press, Reaction Zone Percent BF Cycle Type Hours C.p.s.i.g. Exit gas, ftfi/ Recovered hr. Charged Leaked Picked UpRecovered Through Total 2, 110 1 1, 092 51. 7

Test 2 Charging 10. 0 25 450 0. 17 1, 810 17 0 0 0 Depressurmg. 3. 5 24450-0 0. 379 8 0 0 0 Recovery (e) 16.3 150 0 0.20 0 0 1, 698 78. 5Recovery (t) l1. 7 150 0 0. 25 0 0 24 1. 1

TotaL- 2, 189 25 2, 164 l, 722 79. 6

1 Based on BF: Picked Up.

Example 11 The boron trifiuoride pick-up by the boron halide re- Thisexample utilizes the same processing techniques described in Example Ibut utilizes 60 milliliters of cobaltous fluoride deposited on charcoalas the boron halide reactant.

The cobaltous fluoride is placed in the reaction zone and the same borontrifiuoride-nitrogen mixture utilized in Example I, is passed upflowthrough the reactant at 500 p.s.i.g. and C. After the reaction zone isdepressured to determine if any of the boron trifiuoride reacted couldbe liberated by a pressure difference, the boron trifiuoride recoverycycle is started. The amounts of boron trifiuoride liberated at varioustemperatures are determined while flushing with high surfacesodium-dried nitrogen.

The boron trifiuoride pick-up by the boron halide reactant is calculatedfrom the amount of nitrogen exiting from the reaction zone minus anyboron trifiuoride contained therein. The amount of boron trifiuoridepicked up during the depressuring portion of the cycle is included inthe total boron trifiuoride pick-up. In all cases, this gas is passedthrough a series of stainless steel containers containing iced water.The resulting scrubber solutions are analyzed for boron content byspectrophotometric measurement of the absorbance of the complex ofcarminic acid and boron.

The boron trifiuoride is substantially removed from the borontrifiuoride-nitrogen mixture at 40 C. and 500 p.s.i.g. by passage overthe cobaltous fluoride. No boron trifiuoride is liberated by releasingthe pressure of 500 p.s.i.g. to atmospheric. Satisfactory recovery ofthe boron trifiuoride is accomplished at a temperature of about 150 C.and atmospheric pressure. The cobaltous fluoride is thereby regeneratedfor re-use.

Example 111 This example illustrates the effectiveness of the presentinvention in separating and recovering boron halide from a substantiallyanhydrous fluid mixture comprising a liquid hydrocarbon and borontrifiuoride. The same actant is calculated from the amount of nitrogenexiting from the reaction zone minus any boron trifiuoride containedtherein. The amount of boron trifiuoride picked up during thedepressuring portion of the cycle is included in the total borontrifiuoride pick-up. In all cases, this gas is passed through a seriesof three stainless steel containers containing iced water. The resultingscrubber solutions are analyzed for boron content by spectrophotometricmeasurement of the absorbance of the complex of carminic acid and boron.

The boron trifiuoride is substantially removed from the borontrifiuoride-benzene mixture at 50 C. and 500 p.s.i.g. by passage overthe ferrous fluoride. No boron trifiuoride is liberated by releasing thepressure of 500 p.s.i.g. to atmospheric. Satisfactory recovery of theboron trifiuoride is accomplished at a temperature of about C. andatmospheric pressure. The ferrous fluoride is thereby regenerated forre-use.

Example IV This example illustrates the effectiveness of the process ofthe present invention in separating and recovering a boron halide from asubstantially anhydrous fluid mixture comprising a liquid hydrocarbonand boron trifluoride. The same general processing techniques utilizedin the preceding examples are also used in this example.

Sixty milliliters of the boron halide reactant, namely manganesedifluoride deposited on charcoal, is placed in the reaction zone. Thesubstantially anhydrous liquid hydrocarbon containing boron trifiuoride,namely benzene, is passed upflow through the sorbent at 300 p.s.i. and70 C. After depressuring the reaction zone to determine if any of theboron trifiuoride reacted could be liberated by a pressure difference,the boron trifiuoride recovery cycle is started. The amounts of borontrifiuoride liberated at various temperatures are determined whileflushing with high surface sodium-dried nitrogen. As before, the borontrifluoride pick-up by the boron halide reactant is calculated from theamount of nitrogen exiting from the reaction zone minus any borontrifluoridecontained 'therein. The amount of boron trifluoride picked upduring the depressuring portion of the cycle is included in the totalboron trifluoride pick-up. In all" cases, this gas is passed through aseries of three stainless steel scrubbers containing iced Water. Theresulting scrubber solutions are analyzed for boron content byspectrophoto- 7 metric measure of the absorbance of the complex carminicacid and boron.

The boron trifluoride is substantially removed from the borontrifluoride-benzene mixture at 70 C. and 300 p.s.i.g. by passage overthe manganese difluoride. No boron trifluoride is liberated by releasingthe pressure of 300 p.s.i.g. to atmospheric. Satisfactory recovery ofthe boron trifluoride is accomplished at a temperature of about 150 C.and atmospheric pressure. The manganese difluoride is therebyregenerated for re-use.

We claim as our invention:

1. A process for the separation and recovery of a free boron halide froma substantially anhydrous gaseous mixture containing the same, whichcomprises contacting said fluid mixture with a halide of a metalselected from the group consisting of the metals in Groups VI, VII andVIII of Period 4 of the Periodic Table at conditions to form a complexof the boron halide and metal halide, and subsequently heating saidcomplex sufficiently to decompose the complex and liberate the boronhalide therefrom.

2. A process for the separation and recovery of free boron fluoride froma substantially anhydrous gaseous mixture containing the same, whichcomprises contacting 8 said fluid mixture with a fluoride of a metalselected from the group consisting of the metals in Groups V1,.

VII and VHI of Period 4 of the Periodic Table at con-- ditions to form acomplex of the boron fluoride and: metal fluoride, and subsequentlyheating said complex.

sufliciently to decompose the complex and liberate the i 6. The processof claim 2 further characterized in that I said metal is manganesedifluoride.

7. The process of claim 2 further characterized in that said metalfluoride is chromous fluoride.

References Cited UNITED STATES PATENTS 2,135,458 11/1938 Schultz 2604992,628,991 2/1953 Schneider et al. 23205 X 3,143,402

8/1964 Hervert et a1. 23-205 X OSCAR R. VERTIZ, Primary Examiner.

G. T. OZAKI, Assistant Examiner.

1. A PROCESS FOR THE SEPARATION AND RECOVERY OF A FREE BORON HALIDE FROMA SUBSTANTIALLY ANHYDROUS GASEOUS MIXTURE CONTAINING THE SAME, WHICHCOMPRISES CONTACTING SAID FLUID MIXTURE WITH A HALIDE OF A METALSELECTED FROM THE GROUP CONSISTING OF THE METALS IN GROUPS VI, VII ANDVIII OF PERIOD 4 OF THE PERIODIC TABLE AT CONDITIONS TO FORM A COMPLEXOF THE BORON HALIDE AND METAL HALIDE, AND SUBSEQUENTLY HEATING SAIDCOMPLEX SUFFICIENTLY TO DECOMPOSE THE COMPLEX AND LIBERATE THE BORONHALIDE THEREFROM.